1. Field of the Invention
The present invention relates to a fuel cell including cell units each formed by stacking an electrolyte electrode assembly and a metal separator. The electrolyte electrode assembly includes a pair of electrodes and an electrolyte interposed between the electrodes. A coolant flow field for allowing a coolant to flow along a separator surface is formed between the adjacent cell units.
2. Description of the Related Art
For example, a solid polymer electrolyte fuel cell employs a membrane electrode assembly (electrolyte electrode assembly) (MEA) which includes an anode, a cathode, and a solid polymer electrolyte membrane interposed between the anode and the cathode. The solid polymer electrolyte membrane is a polymer ion exchange membrane. Each of the anode and the cathode includes an electrode catalyst layer and a porous carbon layer. The membrane electrode assembly and separators (bipolar plates) sandwiching the membrane electrode assembly make up a unit cell. In use, generally, a predetermined number of unit cells are stacked together to form a fuel cell stack mounted in a vehicle.
In general, the fuel cell adopts so called internal manifold structure where supply passages and discharge passages extend through separators in a stacking direction. The fuel gas, the oxygen-containing gas, and the coolant are supplied from the respective supply passages respectively to a fuel gas flow field, an oxygen-containing gas flow field and a coolant flow field along electrode surfaces, and then, the fuel gas, the oxygen-containing gas and the coolant are discharged into the respective discharge passages.
For example, a fuel cell disclosed in Japanese Laid-Open Patent Publication No. 2011-018525 has a stack structure formed by stacking a membrane electrode assembly and a separator. A seal is formed integrally with the membrane electrode assembly. The separator includes an anode plate, a cathode plate and an intermediate plate. As shown in FIG. 27, the anode plate has a laterally elongated rectangular plate.
A fuel gas flow field 1 including a plurality of flow grooves 1a is formed in a surface of the anode plate. At one end of the long side of the anode plate, an oxygen-containing gas discharge passage 2b, a coolant supply passage 3a and a fuel gas supply passage 4a are arranged vertically, and at the other end of the long side of the anode plate, a fuel gas discharge passage 4b, a coolant discharge passage 3b and an oxygen-containing gas supply passage 2a are arranged vertically.
The fuel gas supply passage 4a and the fuel gas discharge passage 4b, and the fuel gas flow field 1 are connected by through holes 5a, 5b. Though not shown, the cathode plate and the intermediate plate have the same structure as the anode plate.